After clearing away the Cold War debris that blocked discussion of Marxism's insights since 1945, we focus on Marxism's core contribution to (1) thinking about and (2) changing modern capitalist society. That contribution is class structure and class struggle. Marxism explores how class struggle exists in capitalism, how it influences all of social life, and how it changes over time. Marxism also envisions the end of class struggles as its social change goal now.